Micrometer with movable anvil

ABSTRACT

A micrometer comprises a frame having an anvil mounting section and a spindle mounting section. A spindle is mounted in the spindle mounting section and an anvil means is mounted to the anvil mounting section. The anvil mounting means is biased for movement relative to the spindle mounting section upon creation of gauging pressure by a workpiece that is being measured between the anvil means and the spindle. Indicating means responsive to the relative movement of the anvil means indicates the application of a predetermined gauging pressure on the anvil means and the moving of the anvil means from a non-measuring position to a measuring position.

nited states Patent [191 Morgan 1 1 Nov. 5, 1974 MICROMETER WITH MOVABLE ANVIL [75] Inventor: Paul A. Morgan, Chicago, Ill.

[73] Assignee: Century Wheels, Inc., Lake Bluff,

[22] Filed: Oct. 5, 1972 [21] Appl. No.: 295,225

Related [1.8. Application Data [63] Continuation-impart of Ser. No. 238,340, March 27,

33/143 R, 143 L, 143 H, 147 R, 148 R, 148 E, 148 F, 149 R-l49 J, 154 R-l54 (1,169 R-l71, DIG. 12; 74/441, 22, 424.8 R, 424.8 A, 491, 496, 499, 504, 509, 89.15; 24/243 CC, 243 LS, 243 A [56] References Cited UNITED STATES PATENTS 2,674,806 4/1954 Saigona 33/166 2.741848 4/1956 Livingston 33/167 FOREIGN PATENTS OR APPLICATIONS 332,769 9/1903 France 33/166 OTHER PUBLICATIONS D. A. Bourne, Digital Micrometcr, IBM Technical Disclosure Bulletin, Vol. 3, No. 1 1, April, 1961, page 54.

Primary Examiner-John W. Huckert Assistant Examiner-J0n W. Henry Attorney, Agent, or FirmSpencer & Kaye [57] ABSTRACT A micrometer comprises a frame having an anvil mounting section and a spindle mounting section. A spindle is mounted in the spindle mounting section and an anvil means is mounted to the anvil mounting section. The anvil mounting means is biased for movement relative to the spindle mounting section upon creation of gauging pressure by a workpiece that is being measured between the anvil means and the spindle. Indicating means responsive to the relative movement of the anvil means indicates the application of a predetermined gauging pressure on the anvil means and the moving of the anvil means from a nonmeasuring position to a measuring position.

27 Claims, 12 Drawing Figures PATENTEDnuv SIHM I 1 snmmr s minimum 5 m 3.845564 Wit? 2 W '5 N1 v N RM 8. I N QMW mm vwm w ma Nm Q N N W 1 i mai MICROMETER WITH MOVABLE ANVIL This application is a continuation-in-part application of my pending application Ser. No. 238,340, filed Mar. 27, 1972, and entitled Micrometer Measuring Devices.

This invention relates to improvements in micrometers, and more particularly relates to improvements for insuring accurate readings of micrometers throughout their life.

In the past, there have been many different types of inicrometersbased on the use of a threaded spindle or micrometer screw to obtain measurements of linear distances. These micrometers, for the most part, have been limited to one inch micrometers, that is, micrometers having a measuring range of at most one inch, as distinguished from the largest measurement that the micrometer can make.

A conventional micrometer includes a threaded spindle or micrometer screw which is longitudinally movable under the control of a nut. Attempts to provide micrometers with a greater than one inch range have met with difficulty because of the inaccuracies inherent in producing a thread of this length by ordinary methods. Further, the threads of the micrometer-screw and nut are subject to wear during use of the micrometer. This wear results in play or a sloppy fit between the micrometer screw and the nut and causes inaccurate micrometer readings.

The prior art has recognized that error is introduced into the micrometer reading by the wear of the threads of the micrometer screw and nut, and has employed various means tocompensate for this wear. Although the prior art has compensated for wear, this compensation has not always achieved a compensation of the error introduced by the wear, and in some cases where the sloppiness is continually compensated for, the error wear usually involves periodic adjustment of the nut on the micrometer screw after a certain amount of wear hasoccurred. Until this periodic adjustment is made, however, the sloppiness caused by the wear produces inaccurate micrometer readings.

Although the prior art has attempted to compensate for wear, the compensation efforts have not been entirely successful because in an ordinary micrometer the wear on the thread of the micrometer screw and nut is uneven so that some portions are worn more than other portions. Ordinarily, compensation is achieved by providing a slotted nut and means for periodically contracting the diameter of the nut so that the theaads of the nut grip the threads of the micrometer screw more tightly. Where uneven wear occurs, the contracting of the diameter of the nut cannot entirely compensate for all of the play caused by the wear because if the nut is contracted until its threads engage the threads of the micrometer screw at a point where the most wear has occurred, then the nut will not allow the remaining portion of th micrometer screw threads that have not been subjected to as much wear to pass freely through the nut. On the other hand, if the nut is contracted to allow the portions of the micrometer screw thread that have not worn to pass freely through the nut during its travel, sloppiness will still be present at that portion of the micrometer screw thread that has been subjected to the The accurate measuring of the distance between two outside points of a workpiece is particularly important when the measuring is to be accomplished on the rotor of a disc brake because accuracy of that measurement determines whether the rotor can be safely used in the braking system of a moving vehicle, such as an automobile. An automobile disc braking system usually comprises a rotor attached to the wheel of the automobile and a plurality of brake pads which are normally positioned in an inactive position closely adjacent theopposed braking surfaces of the rotor. When it is desired to slow or stop a rotation of the wheel of an automobile, a brake operating mechanism is actuated to force the brake pads into frictional contact with the rotor. The frictional contact of the brake pads with the rotor results in a decrease in the rotation of the wheel.

. The braking force exerted by the brake pads on the creases, the effective frictional engagement between it and the brake pads decreases, thereby resulting in a decrease in the ability of the braking system to stop the automobile. Eventually, the thickness of the rotor is decreased to a point where it is subject to failure due to the stresses caused by the frictional forces that are applied to it during the braking action. The minimum thickness that the rotor can have and still be safe for use is known as the discard thickness/and thus it is important to be able to accurately measure the thickness of the rotor to determine whether it has reached the discard thickness. If the thickness of the rotor is less than the discard thickness it must be discarded and replaced with a new rotor.

The introduction of disc brakes for use as the braking mechanism of motor vehicles has resulted in the need for a device which can accurately measure the rotors when they are new and which can determine when the disc brakes have been worn to an unsafe point. The original size of the rotors for disc brakes vary from a fraction of an inch to about two inches in thickness and the discard thickness for each type of rotor also varies. Thus, any instrument that is designed for determining whether a disc brake is still safe must be capable of measuring disc brake rotors at varying thickness from as small as three eighths of an inch to as large as two inches. Further, the braking surfaces of the rotors often have grooves and score marks worn into them, and the rotor thickness at these points must also be measured when considering whether any particular disc brake is safe for continued use.

Further, once a measurement of a disc brake rotor has been obtained, it then must be compared with the discard thickness for that rotor. Due to the large number of makes and models of cars, the introduction of new models that occurs every year, and the correspondingly different size disc brakes for each of these cars, the listing of the discard thickness for each disc brake in an available place where the mechanic testing the disc brake system can readily obtain the discard thickness for the particular car which he is testing and compare it to the actual thickness of the disc brake presents still further problems. It is virtually impossible to remember all of the various discard thicknesses for all of the disc brakes currently in use, and with the increasing use of disc brakes on motor vehicles, a convenient source of this information is necessary to enable the mechanic to accurately and quickly assess the safety of the disc brake being tested.

Applicant has recently overcome many of the disadvantages associated with the manufacture of a two inch micrometer as explained in detail in applicants pending application Ser. No. 238,240, filed, Mar. 27, 1972, and entitled MICROMETER MEASURING DEVICES. According to that application, a micrometer is provided with a novel means for controlling the-movement of the spindle including a control nut extending partially around a longitudinal portion of the threaded section of the spindle and resilient force applying means acting transverse to the axis of the spindle to continuously urge the threads of the spindle and control nut into tight engagement with each other to maintain the roots and crests of the threads of spindle in continuous alignment with the roots and crests of the control nut to provide for accurate readings of the micrometer.

The device described in the above pending application is extremely accurate and provides for accurate measurement when the anvil and spindle are properly aligned on the workpiece that is being measured. However, it is often the case, and especially with measurements made on disc brakes, that the micrometer will be misaligned or canted and not placed in correct measuring position on the workpiece that is being measured. The canting of the micrometer causes severe stresses to be developed on the anvil and the structure supporting the anvil. These stresses distort the support structure and result in inaccurate micrometer readings. In fact, the stresses caused can be so severe that the support structure can be permanently distorted to destroy the reproducability of readings obtainable by the micrometer. Further, the canting of the micrometer can cause damage to the workpiece being measured. These problems of misalignment increase with increases in the size of the micrometer and with a large micrometer, such as one having a two inch measuring range, can be brought about by an almost imperceptible misalignment.

A micrometer is a contact instrument which means that there must be positive contact between the workpiece being measured and the micrometer. ln conventional micrometers the amount of contact or gauging pressure applied to the workpiece is a function of the operator of the micrometer. Each operatorobviously will have a different feel ofthe gauging pressure. Also, the feel of the same operator will vary from one measurement to another. The gauging pressure applied to a workpiece, however, must be the same for each measurement to obtain the same true reading time after time, because almost imperceptible differences in the amount of contact can result in different measurements for the same size workpiece.

The prior art has recognized that the amount of contact plays an important part in obtaining accurate readings and has attempted to insure that the amount of contact is equal for all measurements by providing ratchet controls for the micrometer. Basically, a ratchet control is an overriding clutch that kicks out at a predetermined torque to hold the gauging pressure applied to the workpiece to the same amount for each instrument regardless of human factors. Although ratchet controls theoretically assure that the same gauging pressure will be applied to the workpiece, the use of ratchet controls, in practice, does not result in completely repeatable readings.

There are a number of factors contributing to the ineffectiveness of the ratchet control in assuring uniform gauging pressure. One factor is that mechanical variations exist from one ratchet control to another. Another factor is that the friction of the spindle in the control nut determines the amount of gauging pressure that is applied to a workpiece for a given torque. As the friction increases, more of the torque is required to overcome the friction so that less pressure will be applied to the workpiece. Thus, if the friction varies, different gauging pressures will be obtained even though the ratchet control always kicks out at the same torque. The are many variables which affect the amount of friction of the spindle in the nut, such as the tightness of the nut on the spindle, the wear pattern of the threads of the nut and spindle, and the amount and cleaniness of lubrication of the nut and spindle. Differences in the amount of friction between the nut and spindle as a result of these variables cause different gauging pressures to be attained even though a ratchet control is used. A further factor causing variation in gauging pressure when using a ratchet control is the momentum of the rotating spindle. If the spindle is rotated rapidly, energy will be stored which will be released in the form of extra gauging pressure on the workpiec being measured, even though a ratchet control is being used. These causes of error in readings obtained with the use of a ratchet control have been recognized for many years, and a need exists for a means for insuring the application of the same gauging pressure from one measurement to the next.

In the micrometer described in the above referred to Application Ser. No. 238,340, the spindle has a radially extending pin on the back end of its threaded section. A hollow sleeve having a pair of diametrically opposed longitudinally extending slots is mounted about the threaded section of the spindle and the pin rides in the opposed longitudinally extending slots. The hollow sleeve is rotatable and its rotation produces a corresponding rotation of the spindle. The hollow sleeve is a difficult and expensive part to manufacture, and the assembling of the pin on the end of the spindle and in th longitudinally extending slots of the sleeve is a time consuming procedure.

Accordingly, it is an object of the present invention to provide a micrometer that can withstand the stresses caused by misalignment of the micrometer on a workpiece that is being measured.

A further object of this invention is to provide a micrometer that produces the same amount of gauging pressure for each measurement that it makes.

It is another object to provide a micrometer that visually indicates when the workpiece has been correctly gauged.

It is still another object of this invention to provide a micrometer that has a simplified drive mechanism for rotating the spindle to reduce the expense and assembly time of the micrometer.

Additional objects and advantages of the present invention will be set forth in part in the description which follows and in part will be obvious from the description or can be learned by practice of the invention. The objects and advantages are achieved by means of the instrumentalities and combinations particularly pointed out in the appended claims.

To achieve the foregoing objects and in accordance with its purpose, as embodied and broadly described,

the micrometer of this invention comprises: a frame having an anvil mounting section and a spindle mounting section; a spindle mounted in said spindle mounting section for axial movement; an anvil means mounted to the anvil mounting section and movable relative to the spindle mounting section from a non-measuring position to a measuring position upon the creation of a gauging pressure by a workpiece that is being measured between the anvil means and spindle; and indicating means responsive to the relative movement of the anvil means for indicating movement of the anvil means to the measuring position.

Preferably, first biasing means are provided for biasing the anvil means for movement relative to the spindle mounting section and for maintaining the same amount of gauging pressure at the measuring position for each measurement that the micrometer makes. It is also preferred that the anvil means includes a measuring arm and that the first biasing means be a spring engaged with the measuring arm. The measuring arm preferably is pivotally mounted to the anvil mounting section and the spring urges the measuring arm toward the non-measuring position. Additionally, it is preferred that the anvil mounting section is connected to the spindle mounting section for movement relative thereto and that a second biasing means controls the relative movement of the anvil mounting section to the spindle mounting section and absorbs excess gauging pressure.

Desirably, the indicating means comprises a sensing means and an indicator responsive to the sensing means for indicating movement of the anvil means to the measuring position. Preferably, the sensing means comprises a pair of contacts actuated by movement of the anvil means and the indicator is a light in circuit with the contacts.

In another aspect of the present invention, a micrometer is provided which comprises: a frame having an anvil mounting section and a spindle mounting section; anvil means mounted to the anvil mounting section; a

spindle threadably mounted in the spindle mounting section for axial movement; a gear mounted on the spindle and having gear teeth; and a rotatable drive sleeve having internal gear teeth engaged with the gear teeth of the gear for rotating the spindle and causing it to move axially, the drive sleeve having a control knob mounted externally of the spindle mounting section to enable rotation of the drive sleeve.

Preferably. the internal gear teeth of the drive sleeve have the same shape asthe gear teeth of the gear on the spindle. It is also preferred that the internal gear teeth of the drive sleeve are larger than the gear teeth of the gear to produce a sloppy fit of the drive sleeve with the gear. The internal gear teeth of the drive sleeve preferably extend exteriorly of the spindle mounting section into the control knob to permit the spindle to be withdrawn from the anvil means and to extend exteriorly of the spindle mounting section.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory, but are not restrictive of the invention.

The accompanying drawings illustrate an example of a preferred embodiment of the invention and, together with the description, serve to explain the principles of the invention.

Of the drawings:

FIG. 1 is a perspective view of a micrometer constructed in accordance with the teachings of the present invention showing its use for measuring a disc brake rotor.

FIG. 2 is a longitudinal sectional view of the micrometer of FIG. lwith a front plate of its spindle mounting section and a counter mask for a counter mechanism removed for clarity, and shows the internal mechanisms of the micrometer.

FIG. 3 is a vertical sectional view taken along lines 3+3 of FIG. 2 showing the keying of the spindle to a drive gear.

FIG. 4 is an end view of the micrometer as viewed from the left end of the micrometer of FIG. 1.

FIG. 5 is a partial perspective view of the micrometer of FIG. l and shows the anvil mounting section of the micrometer in greater detail.

FIG. 6 is a vertical sectional view taken along lines 66 of FIG. 2.

FIG. 7 is a perspective view in open position of a front plate and a back plate that form the spindle mounting section of the micrometer of FIG. 1 when the plates are brought together in mating position.

Flg. 8 is an exploded perspective view, partially in section, of a drive mechanism for rotating the spindle of the micrometer.

FIG. 9 is a partial perspective view of a pivotal mounting of the anvil mounting section to the spindle mounting section with the front plate of the spindle mounting section removed for clarity, and shows in phantom line the normal position of the anvil mounting section relative to the spindle mounting section and in full line a pivoted position of the anvil mounting sectron.

FIG. 10 is a perspective view of a plastic support for housing electrical elements in the anvil mountng section of the micrometer.

FIG. 11 is a perspective view of a choker plate used for positioning a counter mechanism in the micrometer.

FIG. 12 is a partial perspective view of an adjusting means for adjusting the resilient pressure of a coil spring used to control the movement of the spindle.

Referring to FIG. 1, the present invention is embodied in a micrometer, generally 10, for measuring the thickness of a rotor, generally 12, of a disc braking system. Rotor 12 comprises two spaced apart annular rotor plates 14 and 16. Rotor plate 14 has an outside frictional surface 18 and rotor plate 16 has an outside frictional surface 20. Frictional brake pads (not shown) are mounted closely adjacent each rotor plate 14 and 16 and are brought into contact with frictional surfaces 18 and 20 when a braking force is required. The thickness d" between the outside frictional surfaces 18 and 20 of rotor plates 14 and 16 is also important in determining the safety of the disc brake'rotor, and the micrometer of the present invention is designed to individually measure the thickness of each of the plates 14 and 16.

In accordance with the present invention, the micrometer includes a frame having an anvil mounting section and a spindle mounting section. As here em- 5 bodied, the frame. generally 21, comprises a spindle mounting section, generally 22, in the form of a housing, and an anvil mounting section, generally 26, connected to the spindle mounting section.

As best seen in FIGS. 1 and 7, spindle mounting section 22 is preferably comprised of a front plate 28 and a back plate 30 which are secured to each other by conventional means, such as by screws 32. (FIG. 1). Front plate 28 and back plate 30 have a number of corresponding elements which are identically shaped, but which are the reverse of each other so that when the plates are brought together, the corresponding elements in each plate are aligned and cooperate to form a final element of spindle mounting section 22. Generally, throughout this specification, a single reference numeral will be used to identify the corresponding elements in each plate and the final element, with an unprimed numeral identifying the final element, a single primed numeral identifying an element of front plate 28 and a double primed numeral identifying the corresponding element of back plate 30. For example, and as seen in FIG. 7, front plate 28 has a semi-circular opening 34 at the top ofa side wall 36, and back plate 30 has a corresponding semi-circular opening 34" at the top of corresponding side wall 36". When front plate 28 and back plate 30 are brought together, semicircular openings 34' and 34" cooperate to form full a full opening 34 (FIG. 2) in side wall 36 of spindle mounting section 22. Generally, the primed and double primed numbers are found with reference to FIG. 7 and the unprimed numbers are found in the remaining figures.

Front plate 28 comprises a first side wall 36', an opposing second side wall 38', a top wall 40, and a front wall 44. Similarly, back plate 30 comprises a first side wall 36", an opposing second side wall 38", a top wall 40", and a back wall 42. Top walls 40' and 40 are each curved and thus form a curved top wall 40 of spindle mounting section 22. The bottoms of front and back plates 28 and 30 are open to form an opening at the bottom of spindle mounting section 22. Spindle mounting section 22, as described in greater detail hereafter, has a number of cavities for receiving the various mechanisms and parts of the present micrometer which are described in detail hereafter.

As best seen in FIGS. 1 and S, anvil mounting section 26 comprises an L-shaped housing having a base, generally 46 and a perpendicularly extending support arm, generally 48, and is defined by an L-shaped front plate 50, an L-shaped back plate 52, a vertical side wall 54 joining the inner ends of the support arms of plates 50 and 52, and a horizontially extending top wall 56 at the bottom of side wall 54 closing the top of base 46. As best seen in FIGS. 4, 5, and 6, front plate 50 and back plate 52 are spaced apart to define an interior opening having a narrow top section 58 which expands into a wider bottom section 60 that begins immediately above top wall 56. Shoulders 62 are formed at the point where the interior opening expands from top section 58 to bottom section 60.

Vertical side wall 54 of anvil mounting section 26 opposes side wall 36 of spindle mounting section 22, and these walls together with top wall 56 of anvil mounting section 26 and an anvil measuring arm, generally 64, secured to the top of front and back plates 50 and 52, form the conventional U-shaped measuring end of the micrometer where the workpiece to be measured is placed. The distance between side wall 36 of spindle mounting section 22 and vertical wall 54 of anvil mounting section is slightly greater than two inches to permit workpieces ranging in length from zero to two inches to be measured by the micrometer of the present invention.

In accordance with the invention, a spindle having a threaded section is mounted in the spindle mounting section for axial movement. As here embodied, and as best seen in FIG. 2, the spindle, generally 66, comprises a smooth cylindrical front measuring section 68 that passes through side wall 36 of spindle mounting section 22 and a back threaded section 70. The front end of measuring section 66 has a spherical measuring tip 72 which can be made from a carbide material or any other suitably hardened material. A bearing 74 is secured in opening 34 at the top of side wall 36 and measuring section 68 passes through this bearing.

A drive gear 76 is mounted within spindle mounting section 22 on measuring section 68 adjacent opening 34 by means of a key 78, best seen in FIG. 3, which rides in a longitudinally extending keyway on the outer surface of measuring section 68 and internal keyway 82 in gear 76. Key 78 is square and made of key stock. As viewed in FIG. 2, key 78 is inserted into keyway 82 of drive gear 76 and keyway 80 of measuring section 68 from the right. Bearing 74 prevents key 78 from further moving to the left into keyway 80 of measuring section 68 and out of keyway 82 of drive gear 76. A choker and calibrating plate, generally 84, and described in greater detail hereafter, is pivotally mounted about spindle 66 adjacent spindle drive gear 76 to prevent key 78 from leaving keyway 82 of drive gear 76 to the right. Rotation of spindle 66 thus produced a corresponding rotation of drive gear 76.

The length of threaded section 70 is slightly greater than two inches to permit spindle 66 to move through a two inch measuring range. Threaded section 70 has a pitch diameter of 0.4050 inches and is provided with 20 threads to the inch of the inclined plane type of thread form. As used herein, the term thread form refers to the profile on cross-section of the thread. Preferably, V-type thread forms are used and the right handed American National Unified thread is particularly preferred.

In accordance with a preferred embodiment of the invention, and as best seen in FIGS. 2 and 8, a spur gear 86 is mounted on the back end of threaded section 70 of spindle 66. Spur gear 86 is preferably made of brass and has sixteen gear teeth 88, a pitch diameter of 0.500 inches, a pressure angle of 149?, a 32 pitch, and a center hole opening of 3/l6 inches.

In accordance with a preferred embodiment of the invention, and as best seen in FIGS. 2 and 8, a spindle drive sleeve, generally 90, having internal gear teeth 92 that mate with teeth 88 of spur gear 86 engages spur gear 86 to drive spindle 66. Spindle drive sleeve 90 includes a control knob 94 on one of its ends and a radially outwardly extending flange 96 on its other end. A cylindrical casing 98 (FIG. 2), formed by a semicylindrical casing 98 (FIG. 7) in front plate 28 of spindle mounting section 22 and a semi-cylindrical casing 98" in back plate 30 of the spindle mounting section, receives drive sleeve 90 and prevents it from moving longitudinally within spindle mounting section 22. Casing 98 has alternating cylindrical ribs 100 and relief areas 102, and is open at both of its ends. One open end of casing 98 is formed in side wall 38 of spindle mounting section 22 and the other open end terminates in a relief area 102. Flange 96 is positioned in this end relief area and abuts against adjacent rib 100. Control knob 94 is positioned exteriorly of spindle mounting section 22 and abuts against side wall 38 of the spindle mounting section.

AS best seen in FIGS. 2 and 8, drive sleeve 90 has a longitudinally extending bore 91 having a plurality of longitudinally extending internal teeth 92 equal in number to and mating with teeth 88 on spur gear 86. Rotation of drive sleeve 90 through control knob 94 thus produces a corresponding rotation of spindle 66, and since spindle 66, as described in greater detail hereafter, rotates under the control of a thread, its rotation causes it to move longitudinally toward or away from anvil measuring arm 64 depending on its direction of rotation. The length of internal teeth 92 is such that threaded section 70 of spindle 66 can extend into drive sleeve 90 sufficiently far to withdraw. measuring section 68 of the spindle from anvil measuring arm 64 a distance at least as great as the largest dimension that is to be measured by the micrometer. Thus, in the present embodiment, the length of internal teeth 92 is slightly larger than 2 inches to permit spindle 66 to be withdrawn 2 inches from measuring arm 64 and enable measurement of 2 inch workpieces.

As best seen in FIG. 2, bore 91 and internal teeth 92 extend exteriorly of spindle mounting section 22 into control knob 94 for a substantial portion of their length, and as here embodied, extend approximately half their length into control knob 94. As a result of bore 91 and internal teeth 92 extending into control knob 94, when spindle 66 is fully withdrawn, a portion of its back threaded section 70 is actually outside of spindle mounting section 22. The use of a drive sleeve having a positive drive portion outside of spindle mounting section 22 enables a reduction in the size of the spindle mounting section needed to house spindle 66.

Internal gear teeth 92 of spindle drive sleeve 91) differ from the teeth on a conventional internal gear which have a different shape than and a close tolerance fit with their mating external gear teeth in that the roots of internal teeth 92 of the present invention have the same shape as the crests of teeth 88 on spur gear 86,

spindle in the drive sleeve.

In accordance with the invention, an anvil means is mounted on the anvil mounting section and is movable relative to the spindle mounting section from a nonmeasuring position to a measuring position upon the creation of a gauging pressure by a workpiece that is being measured between the anvil means and the spindle. As here embodied, and as best seen in FIGS. 1 and 2, an anvil means, generally 104, comprises anvil measuring arm 64 pivotally secured to the top of anvil mounting section 26 and a spherical anvil head 1106 secured to the top of measuring arm 64 by conventional means. Anvil head 106 serves as the reference point from which all measurements are taken. Anvil head 106 is made of a suitably hardened material that resists wear, such as a carbide material, and lies along the line of measurement A" of the workpiece being measured.

As best seen in FIG. 2, measuring arm 64 comprises a top section 108, a center section 110 having a hole 112 through which a pivot pin 114 extends, and a bottom vertically extending section 116 which is offset from top section 1118.

As best seen in FIGS. 1 and 6, vertical side wall 54 of anvil mounting section 26 has a U-shaped cutout 118 at its top. Center section 110 of measuring arm 64 is pivotally mounted in cutout 118 between front wall 50 and back wall 52 about pivot pin 114. Pivot pin 114 has its opposite ends secured in walls 50 and 52. Top section 108 of measuring arm 64 thus extends upwardly out of anvil mounting section 26 and bottom section 116 is substantially enclosed by the anvil mounting section. As best seen in FIG. 2, offset bottom section 116 of measuring arm 64 is spaced from the inside surface of vertical wall 54. Measuring arm 64 normally is in a non-measuring vertical position as shown in full line in FIG. 2, and is movable to a measuring position about pivot pin 114 as shown in phantom line in FIG. 2.

In accordance with a preferred embodiment of the invention, a first biasing means in the form of a spring 120 biases measuring arm 64 for movement relative to spindle mounting section 22 and absorbs normal gauging pressure. Bottom section 116 of measuring arm 64 has a cylindrical recess 122 and spring 120 is mounted within this recess with one of its ends abutting against the inside surface of vertical wall 54 of anvil mountings section 26 and its other end seated in recess 122. Measuring arm 64 is thus biased to continuously urge measuring arm 64 to its vertical non-measuring position and anvil head 106 toward spindle 66.

In a preferred embodiment of the invention, anvil mounting section 26 is pivotally connected to spindle mounting section 22 for relative movement thereto and a second biasing means, generally 124, controls the relative movement of anvil mounting section 26 to spindle mounting section 22 and absorbs excess gauging pressure.

As best seen in FIGS. 2, 5, and 9, a solid cross block 126 is integrally formed with front wall 50 and back wall 52 of anvil mounting section 26 to joint these walls at the bottom portion of base 46 immediately adjacent spindle mounting section 22.

The ends of front plate 50 and back plate 52 of base 46 adjacent spindle mounting section 22 are inclined from their bottom upwardly toward the interior of spindle mounting section 22, and as best seen in FIG. 2 back plate 52 has an inclined end 128 and as best seen in FIG. 9 front plate 50'has an inclined end 130. Cross block 126 has a curved outer end 132 with extends past inclined ends 128 and toward the interior of spindle mounting section 22 and an inner end 134 which extends into the interior of base 46 of anvil mounting section 26. Side wall 36 of spindle mounting section 22 has a curved cutout 136 at its bottom shaped to conform with and receive curved outer end 132 of cross block 126. As best seen in FIG. 7, cutout 136 is formed by a cutout 136' in side wall 36" and a corresponding cutout 136" in side wall 36".

Front wall 44 of spindle mounting section 22 has an opening 138 aligned with the center of cutout 136 and back wall 42 has a similar opening 140. As seen in FIGS. 1, 2, 5, and 9, a pivot pin 142 extends through openings 138 and 140, and through cross block 126 to pivotally mount the cross block, and hence anvil mounting section 26 to spindle mounting section 22. An inclined surface 144 extends upwardly from the top edge of curved cutout 136 toward the interior of spindle mounting section 22 and in normal position this surface mates with the inclined ends 130 and 128 of front and back plates 50 and 52 of anvil mounting section 26. As best seen in FIGS. and 9, the ends of front wall 44 and back wall 42 of spindle mounting section 22 ad-. jacent base 46 of anvil mounting section 26 overlie and cover inclinded ends 128 and 130 and curved outer end 132 of cross block 126. During pivotal movement of anvil mounting section 26, inclined surface 144 of anvil mounting section 26 separates from inclined ends 128 and 130, but the greatest amount of movement permitted is such that front wall 44 and back wall 42 still overlie inclined ends 128 and 130 and curved outer end 132 of cross block 126 so that these parts are not exposed during movement of anvil mounting section 26.

In accordance with a preferred embodiment of the invention, and as seen in FIG. 2, second biasing means 124 comprises a bolt 146, a die spring 148 mounted about the bolt, and an abutment 150 for compressing die spring 148 to absorb excess gauging pressure.

As best seen in FIGS. 2 and 6, bolt 146 is mounted immediately below horizontal wall 56 of anvil mounting section 26 between front and back walls 50 and 52. As seen in FIG. 2, bolt 146 has a smooth shaft 147 which terminates in a first end 152 that passes through an opening 154 in inclined surface 144 of side wall 36 of spindle mounting section 22. The terminal portion of end 152 is threaded. Opening 152 expands into a second larger opening 156 in side wall 36 and a nut 158 is threaded into end 152 in opening 156. Nut 158 has a curved end surface which abuts against a shoulder 160 formed at the point where opening 152 expands into opening 156. End 152 is thus captured within opening 156 of spindle mounting section 22. The opposite end of bolt 146 has a slotted head 162 which serves as a stop for die spring 148.

Die spring 148 is mounted about bolt 146 adjacent slotted head 162 and is characterized by two flat ends which prevent cocking or canting of the spring. Two spring caps, 164 and 166, are positioned between bolt 146 and die spring 148 at each end of the die spring to center the die spring on the bolt. One end of die spring 148 seats against slotted head 152 of bolt 146 while its other end seats against abutment 150. Shaft 147 of bolt 146 passes through an opening in abutment 150. Abutment 150 is fixed to front plate 50 and back plate 52 of anvil mounting section 26 and moves with the anvil mounting section while it pivots about pin 142. Die spring 148 continuously biases anvil mounting section 26 and measuring arm 64 toward spindle mounting section 22.

In accordance with the invention, indicating means responsive to the relative movement of the anvil means is provided for indicating the movement of the anvil means from the non-measuring position to the measuring position. As here embodied, and as shown in FIG. 2, the indicating means comprises a sensing means, generally 168, for sensing movement of the anvil means, and an indicator in the form of a light 170, responsive to the sensing means for indicating movement of the anvil means to a measuring position.

Sensing means 168 includes a first contact 172 connected to measuring arm 64 and a second contact 174 mounted to vertical wall 54. Measuring arm 64 has a threaded hole 176 transversely extending completely through bottom section 116 below recess 122. A screw 178 having a slotted head on one end is received in this hole and contact 172 is mounted on the opposite end of the screw. An L-shaped metal bracket 180 is secured to the inside surface of vertical side wall 54 of anvil mounting section 26, but is electrically insulated therefrom by conventional means, such as by a plastic insulating sheet 182 positioned between the wall and bracket. Insulating sheet 182 is secured to wall 54 by a suitable adhesive such as an epoxy adhesive, and bracket 180 is similarly secured to the opposite side of the sheet. Second contact 174 is mounted at the top of bracket 180 and is normally spaced from and aligned with first contact 172.

Light is in electric circuit with contacts 172 and 174 and is mounted in a socket 184 formed in a plastic support 186. Support 186 is removably insertable into the base 46 of anvil mounting section 26 between front plate 50 and back plate 52 and has an outer peripheral shape which conforms to the outer shape of base 46. As best seen in FIGS. 2 and 10, support 186 has a cavity 188 for receiving a power source in the form of two batteries 190 and 192 which are connected in series one above the other by a metal strip 194.

Support 186 has a horizontally extending overhang 196 at one end which fits over inner end 134 of cross block 126 when the support is property located in anvil mounting section 26. Support 186 has an upwardly extending projection 198 at its other end which abuts against shoulders 62 of front plate 50 and back plate 52 of anvil mounting section 26. As best seen in FIGS. 4, and 10 support 186 has two aligned projecting semicircular locking spheres 200, one on each side of the support. Spheres 200 are engageable in aligned detent openings 201 in front plate 50 and back plate 52 to firmly position support 186 in mounting section 26. Support 186, however, can be partially removed from anvil mounting section 26 by applying pressure to projection 198 to overcome the detent force and pivot the support about cross block 126 to expose cavity 188 and socket 184 and enable replacement of batteries 190 and 192 and light 170.

Light 170 is connected to bracket by an electric lead 202 and is connected to battery by a second lead 204. A third lead 206 connects battery 192 to screw 178. As bestseen in FIGS. 1, 4, and 5, front plate 50 and back 52 of anvil mounting section 26 each have a plastic dome 208 adjacent light 170 so that when light 170 is actuated, it is visible from either side of the micrometer.

In accordance with a preferred embodiment of the invention, a direct reading counter mechanism is connected to the spindle. As here embodied, and as shown in FIG. 2, a conventional counter mechanism, generally 210, is mounted within spindle mounting section 22 adjacent side wall 36. Counter mechanism 210 includes a U-shaped counter frame 212 having parallel ends 214 and 216 and four counting wheels 218, 220, 222, and 224 which are all mounted on a rotatable common drive shaft 226 extending through ends 214 and 216 of frame 212. Drive shaft 226 is operatively connected to counting wheel 224 which indicates the lowest unit of measurement of the micrometer. Rotation of drive shaft 226 thus produces a corresponding rotation of counting wheel 224. Counting wheels 218, 220, and

222, however, are normally prevented from rotating when drive shaft 226 is rotated, and instead are actuated by counting wheel 224. Front wall 44 of front plate 28 has a window 228 (FIGS. 1 and 7) which contains a clear plastic. Window 228 is positioned over the counting wheels to permit the indicia on them to be easily viewed. A counter mask 229 (FIG. 1) covers counter mechanism 210, but has openings to permit the indicia on the counting wheels to be viewed through window 228 of front plate 28.

A counter drive gear 230 is fixed to the end of drive shaft 226 adjacent end 216 of frame 212 so that rotation of drive gear 230 produces a rotation of drive shaft 226 and actuation of the counting wheels. Counter drive gear 230 is connected to drive gear 76 mounted on measuring section 68 of spindle 66 by an intermediate transmission gear 232 which has a two gear cluster, one of which is engaged with drive gear 76 and one of which is engaged with countEr drive gear 230.

As best seen in FIG. 7, back wall 42 of back plate 30 has two spaced apart end support blocks 234 and 236, and parallel ends 214 and 216 of counter mechanism 116 are mounted on these blocks. Back wall 42 also contains a drive shaft support block 238 having a central opening 240 (FIG. 7). Front wall 44 of front plate 28 has first and second shaft positioning blocks 242 and 244 which mate with the ends of drive shaft support block 238. Drive shaft 226 of counter mechanism 210 has one of its ends mounted in opening 240 of drive shaft support block 238 and its other end held by choker plate 84 so that the counter mechanism is maintained in proper position in spindle mounting section 22. Choker plate 84 positions counter mechanism 210 in spindle mounting section 22 by means of an arcuate slot 246 (FIG. II) which engages one end of drive shaft 226 when the choker plate is in operating position. Choker plate 84 can be easily disengaged from drive shaft 226 by pivoting it around spindle 66 when front plate 28 is removed from back plate 30. Counter mechanism 210 can then be easily lifted out of drive shaft support block 238 and disengaged with intermediate gear 232 to permit the counter mechanism to be calibrated.

Choker plate 84 also functions to keep gears 76 and 232 from binding when spindle 66 is withdrawn from the measuring end of the micrometer. When spindle 66 is rotated so as to withdraw measuring section 68 from anvil head 106 a back pressure is created on drive gear 76 which tends to force it against the side of gear 232, and thereby bind gears 76 and 232 against each other and prevent further withdrawal of spindle. Choker plate 84, however, opposes this binding force and permits spindle 66 to be easily withdrawn without binding. A straight keeper wire 248 is positioned between a block 252, described in greater detail hereafter, and choker plate 84 to apply pressure to the choker plate to enable it to overcome the binding back pressure of the gears.

In accordance with a preferred embodiment of the invention, a control nut is provided for controlling movement of the spindle. The control nut extends partially around a longitudinal portion of the threaded section of the spindle and has threads mating with those of the threaded section of the spindle. As here embodied, and as shown in FIG. 2, the control nut comprises a first half nut 250 which extends around a top longitudinal portion of threaded section 70 of spindle 66. Half nut 250 has V-type American National Unified Thread forms which mate with the thread forms of spindle 66. Half nut 250, as best seen in FIG. 8, has a curved top and this top fits within the curvature of top wall 40 of spindle mounting section 22. A locating and retaining block 252 (FIG. 2) formed by a block 252' in front plate 28 and a block 252" in back plate 30 is spaced from the inner end of casing 98 and half nut 250 is mounted in the space between casing 98 and block 252. Block 252 has an opening 254 and spindle 66 passes through this opening.

In a preferred embodiment of the invention, the threaded length of the control nut is about twice the pitch diameter of threaded section 70 of spindle 66. The provision of a threaded length which is twice the pitch diameter of spindle'66 spreads and distributes the wear between the spindle and control nut over a greater length and reduces the wear on any one threaded portion. It has been found that a threaded length for the control nut of at least twice the pitch diameter of spindle 66 is the minimum length which will be effective in markedly reducing wear on the threads, and thus it is highly desirable to provide such a relationship in the micrometer of the present invention.

In accordance with a preferred embodiment of the I invention, resilient force applying means acts transverse to the axis of the spindle to continuously urge the mating threads of the spindle and control nut into tight engagement with each other to maintain the roots and crests of the threads of the spindle in continuous alignment with the roots and crests of the control nut and provide for accurate readings of the micrometer.

As here embodied, this force applying means acts perpendicularly to the axis of spindle 66 and comprises a second nut means in the form of a second half nut 256 which is aligned with and opposes first nut 250, and a biasing means in the form of a resilient coil spring 258 engaged with second nut 256. First nut 250 and second nut 256 are spaced from each other about the circumference of threaded section 70 of spindle 66 and are continuously urged toward each other by coil spring 258, but are sized so that they do not engage each other.

As best seen in FIGS. 2 and 8, half nut 256 has a centrally located circular recess 260 on its bottom surface 262. Coil spring 258 has its top end seated in recess 260 and its bottom end seated in a slotted end 264 of a screw 266. Screw 266 is threadably mounted in a pair of nuts 268 and 270 that are separated by a washer. A pair of opposing U-shaped members 274 and 275 (FIG. 2) formed by members 274' and 275 in front plate 28 and members 274" and 275" in back plate 30 are positioned below half nut 256 and form a cavity which retains nuts 268 and 270 in spindle mounting section 22 and prevents then from moving when a screw 266 is turned into nuts 268 and 270.

As best seen in FIG. 12, a straight cross-leg 277 extends from and diameterically intersects the bottom coil of coil spring 258, and this cross-leg is seated in screw 266. Screw 266 is identically slotted at both of its ends to permit either end of the screw to be inserted into nuts 268 and 270 when the micrometer is assemmoving from the housing a magazine, generally 276, described in greater detail hereafter. Because cross-leg 277 is diametrically positioned on coil spring 258 and recess 260 is at the center of half nut 256, the resilient pressure of the coil spring is evenly distributed to bottom half nut 256 to enable it to respond evenly to changes in the thread of spindle 66. Second nut 256 is a freely floating nut and its longitudinal axis is free to rock radially with respect to the axis of spindle 66.

In a preferred embodiment of the invention, the length of the threads of second nut 256 is greater than twice the pitch diameter of spindle 66 to more evenly distribute the wear on the threads of second nut 256 and spindle as discussed above.

The operation of the micrometer in compensating for wear and adjusting for error introduced by the wear is described in detail in applicants above referred to pending application Ser. No. 238,240 and this application is hereby incorporated by reference. Briefly, the resilient pressure of coil spring 258 acting perpendicular to the axis of spindle 66 forces control nut 250 and spindle 66 together to maintain their roots and crests in continuous longitudinal alignment. Second nut 256 moves with coil spring 258 in response to any changes in the size of a particularly thread, so that a large portion of the pressure caused by the larger thread will be resiliently absorbed by coil spring 258 and will not cause wear.

In this embodiment of the invention, nuts 250 and 256 are both movable and free to move in a longitudinal direction during movement of spindle 66. To obtain accurate and reproducible measurements, at least one of these nuts must be at a set distance from anvil head 106 when the anvil head and measuring arm 64 are in their measuring position as shown in phantom line in FIG. 2. Thus, means are provided for positioning control nut 250 at a set longitudinal distance from anvil head 106 when measuring arm 64 is in its measuring position. As here embodied, this means is the inner end of casing 98. Casing 98 aids in positioning both nuts 250 and 256 at a set distance from anvil head 106 because when spindle 66 engages a workpiece, a back pressure is created which is transmitted to nuts 250 and 256. When the back pressure is created, nuts 250 and 256 move longitudinally until they contact the end of casing 98 which is longitudinally fixed and thereby positions the nuts in the same longitudinal alignment whenever a measurement is made.

In this embodiment of the invention, and as best seen in FIG. 2, a magazine 276 is mounted below counter mechanism 210 between side walls 36 and 38 of spindle mounting section 22. Magazine 276 includes a frame, generally 278 having two opposed outside walls 280 and 282, a bottom wall 284, a top wall 286, a back wall 288, and a front wall 290. A floor plate 292 provides a hand grip for grasping magazine 276 so that it can be inserted into or removed from the open bottom of spindle mounting section 22.

Front wall 290 is made of transparent plastic to enable an information tape 294 to be viewed from the front of the magazine. Tape 294 is wound on two spaced apart spools 293 and 295 that are journaled for rotation in magazine 276. An inner side wall 296 is spaced from outside wall 280 of magazine 276 and spools 293 and 295 are journaled in this inner wall and outside wall 282 through drive pins 298 and 300. As best seen in FIGS. 5 and 7, a slot 297 is formed in side wall 36. Slot 297 serves as a guide for drive pins 298 and 300 adjacent outside wall 282 of magazine 276.

Spools 293 and 295 are connected to each other by a positive drive means so that rotation of one of the spools produces an equal and corresponding rotation of the other. As here embodied, a rotatable member in the form of a drive gear 302 is secured to drive pin 298 between inner wall 296 and outside wall 280 of magazine 276. Similarly, a second rotatable member in the form of a drive gear 304 is secured to drive pin 300 between inner wall 296 and outside wall 280. A series of intermediate gears connect drive gears 302 and 304 so that rotation of drive gear 302 produces a rotation of drive gear 304 and of spools 293 and 295. The provision of a positive drive for both spools aids in obtaining an even drive to tape 294. As will be apparent to those skilled in the art other means can be used to provide a positive drive, such as, for example, a bead chain, sprocket chain or ladder chain and appropriate rotatable members for these chains.

In accordance with a preferred embodiment of the invention, a connecting means in the form of a straight pin 312 is attached off center to drive gear 302, but parallel to the axis of drive pin 298, for inserting magazine 276 in spindle mounting section 22 and connecting it to a magazine drive means. As best seen in FIG. 2, the magazine drive means includes a magazine drive plate, generally 314, which opposes drive gear 302 of magazine 276.

A rotatable control knob 316 is mounted externally of spindle mounting section 22 in alignment with drive gear 302. Control knob 316 has a shaft (not shown) which extends through wall 38 of spindle mounting section 22 and magazine drive plate 314 is fixed to this shaft internally of the housing. Drive plate 314 has at least one radially extending slot 318 which begins at its outer edge and when magazine 276 is in operative position in spindle mounting section 22, pin 312 is engaged in one of these slots. Rotation of control knob 316 causes drive plate 314 to rotate and because pin 312 is engaged in a slot 318 of the drive plate, drive gear 302 will also rotate. This rotation of drive gear 302 produces a corresponding rotation of spools 293 and 295 thereby moving tape 294. Magazine 276 can be inserted into spindle mounting section 22 and connected to magazine drive plate 314 by having pin 312 engage slot 318. If magazine drive plate 314 is not in a position where its slot 318 is aligned with pin 312, it can be rotated by control knob 316, to bring its slot into aligned position with pin 312. Outside wall 280 has a circular opening (not shown) at its top to permit pin 312 to rotate with drive gear 302 and be connected to magazine drive plate 314.

Tape 294 is divided longitudinally into sections, with each section listing a car model, car year, and discard thickness for the disc brake rotor for that car. Each section of tape 294 is in alphabetical order so that the discard thickness for a particular car can easily be determined by rotating the tape until the desired section appears in a window 320 (FIGS. 1 and 7) of front plate 28 of spindle mounting section 22. Window 320 contains a clear plastic. The disc brake rotor size is then determined by miking the rotor, and this size is compared to the discard thickness indicated on the magazine. If the actual micrometer size is larger than the discard thickness, the rotor can still be used, but if it is smaller, the rotor is unsafe and should be discarded and 17 replaced. Upon introduction of a new model year, magazine 276 can be removed, and replaced with a new magazine having a new tape with the revised information for the new model year.

The length of tape 294 needed for storing all of the information necessary in readily viewable size to determine the thicknesses of rotors for all of the various years, makes and models of cars is approximately six feet and preferably feet. This length of tape cannot be easily wound on spaced apart spools and be freely rotated from one end to another on these spools in a magazine without having the tape sag, bunch up, or jam. In one aspect of the present invention tape 294 is made of a plastic film having elastic recovery so that a spring-like action is provided on the magazine spools which together with the direct drive of both spools enable six to ten feet of tape to evenly move from one spool to another without any winding problems. Suitable tapes for this purpose can be made of any plastic film which is resilient and exhibits elastic recovery. Thus, differentially stressed spring-like plastic films of, for example, polyethylene terephthalate (sold under the trademark Mylar by du Pont Company) polyamides (e.g. nylon), polyacrylonitrile, and copolymers of acrylonitrile with other vinyl compounds, copolymers of vinyl chloride and vinylidene chloride, and polyhydrocabrons (e.g. polyethylene and polypropylene can be used in making tapes 294. The resilient nature of tape 294 tends to force it against front wall 290 of magazine 276 so that the plane of the tape is parallel to the plane of front wall 44 of front plate 28. Tape 294 thus tends to ride against front wall 290. The resilient nature of tape 294 also permits the rotating force of drive gear 302 to be transmitted to the tape without any lost motion so that the tape immediately responds to rotation of drive 302 in an even manner.

It will be apparent to those skilled in the art that the micrometer of the present invention can be used to measure workpieces other than disc brake rotors without departing from the scope of this invention. Accordingly, the information on tape 294 can be tailored for use with other systems where it is important to have a readily available source of indicating measurements. The micrometer of the present invention is extremely accurate, and its counting wheel 224 is provided with ten equally spaced digits for reading in thousandths of an inch. The present invention thus provides a micrometer of two inch capacity reading to thousandths of an inch on one line, in a single final group of numbers in which no verniers need be scrutinized. Of course, the micrometer can be made to read in dimensions other than inches, such as for example millimeters.

In accordance with a preferred embodiment of the invention, locking means are provided on the magazine to lock it into position in spindle mounting section 22.

As here embodied, and as shown in FIG. 2, this means comprises a flat leaf spring 322 that is secured to outside wall 280 of magazine 276. Leaf spring 322 comprises an anchor leg 324 attached to outside wall 280, and a downwardly extending locking leg 326 that is angled away from outside wall 280 and toward side wall 38 of spindle mounting section 22. Side wall 38 has an inner lip 328 and when magazine 276 is inserted far enough into spindle mounting section 22, locking leg 326 of leaf spring 322 engages this lip and prevents the magazine from being removed from the spindle mounting section. Top wall 286 of magazine 276 abuts against U-shaped member 274 and 275 when locking leg 326 engages lip 328 to prevent movement of the magazine within spindle mounting section 22. A keyway 330 is provided in side wall 38 adjacent the locked position of leaf spring 322. When it is desired to remove magazine 276 from spindle mounting section 22, a key 332, such as a house key or car key, is inserted into keyway 330 to depress locking leg 326 clear from lip 328. While locking leg 326 is depressed, magazine 276 can be grasped by floor plate 292 and removed from spindle mounting section 22. When inserting magazine 276 into spindle mounting section 22 locking leg 326 cannot lock into lip 328 until connecting pin 312 engages in magazine drive plate 314.

The operation of the micrometer in withstanding the stresses developed during measurement and in providing the same gauging pressure for each measurement that it makes will now be described. A workpiece is positioned between measuring arm 64 and spindle 66 and control knob 94 is rotated to advance the spindle toward the measuring arm. When spindle 66 advances to the point where its tip 72 and anvil head 106 of measuring arm 64 both contact the workpiece, a gauging pressure develops. The advance of spindle 66 is continued, but contrary to conventional micrometers where all of the force of the gauging pressure is concentrated on the anvil as the spindle is advanced as a result of the anvil being fixed and where the final amount of gauging pressure is a function of the operator of the micrometer, measuring arm 64 of the present invention, and hence anvil head I06, move about pivot 114 to their measuring position illustrated in phantom line in FIG. 2, under the control of spring which absorbs energy and thus lessens the amount of gauging pressure that is developed on the anvil. Spring 120 is under an initial slight predetermined compression when measuring arm 64 is in its vertical non-measuring position, illustrated in full line in FIG. 2, and the gauging pressure developed by the advancement of spindle 66 must overcome this compression before measuring arm 64 begins its movement about pin 114. As measuring arm 64 moves about its pivot 114, spring 1220 comes under greater compression and the gauging pressure on the workpiece increases. The gauging pressure for any given position of measuring arm 64, however, is constant due to the action of spring 1120. Thus, when measuring arm 64 reaches its measuring position, the gauging pressure at this position is always the same. When measuring arm 64 reaches its measuring position, contact 172 at the bottom of the measuring arm engages contact 174 on bracket 180 to close the electrical circuit to light and actuate the light. When light 170 is actuated, it is visible through domes 208 from either side of the micrometer to provide a visual indication of when measuring arm 64 reaches its measuring position and the correct gauging pressure is produced. Ordinarily, the operator cannot stop rotating spindle 66 at the instant that light 170 is actuated, and measuring arm 64 will move a slight distance past its measuring position. To insure that measuring arm 64 is at its measuring position when a reading is taken, spindle 66 is slowly withdrawn causing spring 120 to move measuring arm 64 slowly about pivot 114 in an opposite direction to bring the measuring arm back to its measuring position. Rotation of spindle 66 is continued until contact 172 disengages from contact 174 breaking the electrical circult and deactuating light 170. The micrometer reading is now read.

The gauging pressure of the micrometer of the present invention when measuring arm 64 is in its measuring position can be set and maintained at a relatively low level by the selection of a spring having appropriate spring characteristics and can be as low as 6-10 p.s.i. In contrast, gauging pressures developed by conventional micrometers on the anvil can be in the range of 20,000 p.s.i. to 30,000 p.s.i., especially when the micrometer is misaligned. ln the present invention, excessive gauging pressures caused by misalignment or canting of the micrometer on the workpiece are prevented from developing by die spring 148 of second biasing means 124. As just discussed, measuring arm 64 can move past its measuring position a slight distance, but this movement is due to the inherent elastic properties of contacts 172 and 174 and their supporting structure so that only a small movement is possible before a nonresilient coupling of measuring arm and bracket 180 is produced whereupon the gauging pressure would begin to increase rapidly and cause a high stress concentration on anvil head 106 and measuring arm 64. Spring 120 cannot absorb this pressure because the further compression of the spring necessary to absorb it is prevented by the non-resilient coupling of measuring arm 64 and bracket 180. As soon as the gauging pressure develops to overcome an initial compression on die spring 148 which normally urges anvil mounting section 26 toward spindle mounting section 22, the die spring begins to compress and absorb energy and thus lessen the amount of gauging pressure developed on anvil head 106. Anvil mounting section 26 is pivotable about pivot 142, and moves about pivot 142 from its normal position (FIG. 9 phantom line position) where ends 128 and 130 of back plate 52 and front plate 50 abut against inclined surface 144 of side wall 36 of spindle mounting section 22, away from spindle mounting section 22 to a position where ends 128 and 130 do not abut against inclined surface 144 (HO. 9 full line position), when measuring arm 64 couples to bracket 180. Abutment 150 moves with anvil mounting section 22 and compresses die spring 148 against slotted head 162 of bolt 146 to enable the die spring to absorb energy and prevent excessive gauging pressures from developing even though the micrometer in misaligned or canted on the workpiece. Die spring 148 is a spring which can absorb large amounts of energy. As soon as the force that causes die spring 148 to compress is lessened, the die spring begins returning anvil mounting section 26 to its normal position where ends 128 and 130 of back plate 52 and front plate 50 abut against inclined surface 144 of side 36 of spindle mounting section 22. When anvil mounting section 26 returns to its normal position the micrometer is ready to be used in its normal manner. Second biasing means 124 thus prevents excess concentrations of stress from developing on anvil head 106 which can cause permanent distortion of the parts of the micrometer. Second biasing means 124 together with spring 120 provide a biasing means which acts to insure that the same gauging pressure is obtained for each measurement the micrometer makes and which prevents the development of excess gauging pressures which can destroy the reliability of the micrometer.

The present invention thus provides a micrometer which insures that the same gauging pressure is applied to a workpiece for each measurement that the micrometer makes, provides a visual indication of when the micrometer reading should be taken, insures that excess gauging pressure does not develop on the anvil of the micrometer as a result of misalignment or other causes, and provides a positive, easily assembled, means for driving the spindle. The various features of the present invention are especially useful with micrometers having a two inch measuring range, such as the micrometers described in the above referred to application Scr. No. 238,340, because these micrometers can more easily generate large stresses on the anvil.

The present invention also provides a micrometer which is particularly useful in measuring disc brake rotors and because of the spring biasing of measuring arm 64 can withdraw the spherical measuring tip 72 on spindle 66 and the spherical anvil head 106 from the depth of grooves worn into disc brake rotors up to the smooth surfaces of the rotors without damage to the micrometer. The use of spherical ball contact ends comprising anvil head 106 and measuring tip 72 enables the micrometer of the present invention to measure scored or deeply worn sections of the rotor regardless of the relative positions of the deep scores on each side of the rotor.

This invention in its broader aspects is not limited to the specific details shown and described and departures may be made from such details without departing from the principles of the invention and without sacrificing its chief advantages.

What is claimed is:

l. A micrometer for measuring a workpiece comprismg:

a. a frame having an anvil mounting section and a spindle mounting section, the anvil mounting section being connected to the spindle mounting section for relative movement thereto;

b. a spindle mounted in said spindle mounting section for axial movement;

c. an anvil means mounted to said anvil mounting section and movable relative to said spindle and anvil mounting sections from a non-measuring position to a measuring position upon the creation of a gauging pressure by a workpiece that is being measured between the anvil means and the spindle;

d. indicating means responsive to the relative movement of the anvil means for indicating movement of said anvil means to the measuring position;

e. a first biasing means for biasing said anvil means for movement relative to said mounting sections and for maintaining the same amount of gauging pressure at said measuring position for each measurement that the micrometer makes; and a second biasing means connecting said mounting section and spindle mounting section for controlling the relative movement of the anvil mounting section to the spindle mounting section and absorbing gauging pressure in excess of that which can be absorbed by said first biasing means.

2. The micrometer of claim 1 wherein said anvil means includes a measuring arm and said biasing means is a spring engaged with said measuring arm.

3. The micrometer of claim 2 wherein said measuring arm is pivotally mounted to said anvil mounting section and said spring urges said measuring arm toward said non-measuring position.

4. The micrometer of claim 1 where said anvil mounting section is pivotally connected to said spindle mounting section.

5. The micrometer of claim 4 wherein said second biasing means comprises a bolt mounted in said anvil mounting section and having one end captured in said spindle mounting section, a spring mounted about said bolt in said spindle mounting section, and an abutment fixed to and movable with said anvil mounting section for compressing said spring to absorb excess gauging pressure.

6. The micrometer of claim 1 wherein said indicating means comprises a sensing means for sensing movement of said anvil means and an indicator responsive to said sensing means for indicating movement of the anvil means to the measuring position.

7. The micrometer of claim 6 wherein said sensing means comprises a pair of contacts actuated'by movement of said anvil means, and said indicator is a light in circuit with said contacts.

8. The micrometer of claim 1 wherein said indicating means comprises an electric circuit including a light operated upon movement of said anvil means to the measuring position.

9. The micrometer of claim 1 including a gear mounted on said spindle and having gear teeth, and a drive sleeve having internal gear teeth engaged with the gear teeth of said gear for rotating the spindle and causing it to move axially, said drive sleeve having a control knob extending exteriorly of said spindle mounting section to enable rotation of the drive sleeve.

10. The micrometer of claim 9 wherein the portions of the internal gear teeth of the drive sleeve and the portions of the gear teeth of said gear that mate with each other have the same shape.

11. The micrometer of claim 10 wherein said intermal gear teeth are larger than the gear teeth of the gear to produce a sloopy fit of the drive sleeve with said gear.

12. The micrometer of claim 9' wherein the internal gear teeth of the drive sleeve extend exteriorly of the spindle mounting section into the control knob to permit the spindle to be withdrawn from the anvil means and to extend exteriorly of the spindle mounting section.

13. The micrometer of claim 1 wherein the spindle has a threaded section, a control nut extends partially around a longitudinal portion of the threaded section and has threads mating with those of the threaded sec tion of the spindle, and resilient force applying means acts transverse to the axis of the spindle to continuously urge the mating threads of the spindle and control nut into engagement with each other to maintain the roots and crests of the threads of the spindle in continuous longitudinal alignment with the roots and crests of the control nut and provide for accurate readings of the micrometer.

14. The micrometer of claim 13 wherein the resilient force applying means comprises a floating nut means spaced from, non-engaging with, and opposing said control nut and having threads mating with those of said threaded section, and a biasing means engaged with said nut means for urging said nut means against said spindle.

15. The micrometer of claim 14 wherein the biasing means engaged with said nut means is a coil spring.

16. The micrometer of claim 14 including means for positioning said control nut at a set longitudinal distance from said anvil means when said anvil means is in its measuring position.

17. A micrometer for measuring a workpiece comprising:

a. a frame having an anvil mounting section and spindle mounting section;

b. anvil means mounted to said anvil mounting section;

c. a spindle threadably mounted in said spindle mounting section for axial movement;

d. a gear mounted on said spindle and having gear teeth; and

e. a rotatable drive sleeve having internal gear teeth engaged with the gear teeth of said gear for rotating said spindle and causing it to move axially, said drive sleeve having a control knob mounted externally of said spindle mounting section to enable rotation of the drive sleeve.

18. The micrometer of claim 17 wherein the portions of the internal gear teeth of the drive sleeve and the portions of the gear teeth of said gear that mate with each other have the same shape.

19. The micrometer of claim 18 wherein said internal gear teeth are larger than the gear teeth of the gear to produce a sloppy fit of the drive sleeve with said gear.

20. The micrometer of claim 17 wherein the internal gear teeth of the drive sleeve extend exteriorly of the spindle mounting section into the control knob to permit the spindle to be withdrawn from the anvil means and to extend exteriorly of the spindle mounting section.

21. The micrometer of claim 17 wherein the spindle has a threaded section a control nut extends partially around a longitudinal portion of the threaded section and has threads mating with those of the threaded section of the spindle, and resilient force applying means acts transverse to the axis of the spindle to continuously urge the mating threads of the spindle and control nut into tight engagement with each other to maintain the roots and crests of the threads of the spindle in continuous longitudinal alignment with the roots and crests of the control nut and provide for accurate readings of the micrometer.

22. The micrometer of claim 21 wherein the resilient force applying means comprises a floating nut means spaced from, non-engaging with, and opposing said control nut and having threads mating with those of said threaded section, and a biasing means engaged with said nut means for urging said nut means against said spindle.

23. A micrometer for measuring a workpiece comprising:

a. a frame having an anvil mounting section and a spindle mounting section, said anvil mounting section being connected to said spindle mounting section for relative movement thereto;

b. a spindle mounted in said spindle mounting section for axial movement;

c. an anvil means mounted to said anvil mounting section and movable relative to said spindle mounting section from a non-measuring position to a measuring position upon the creation of gauging pressure by a workpiece that is being measured between the anvil means and the spindle, said anvil means including a measuring arm comprising a top section extending above the anvil mounting section and having an anvil head mounted thereon, said measuring arm further including a center section, means pivotally mounting said center section to the anvil mounting section and a bottom section offset from the top section and substantially enclosed by said anvil mounting section;

d. indicating means responsive to the relative movement of the anvil means for indicating movement of said anvil means to the measuring position; and

acts transverse to the axis of the spindle to continously urge the mating threads of the spindle and control nut into tight engagement with each other to maintain the roots and crests of the threads of the spindle in continuous longitudinal alignment with the roots and crests of the control nut and provide for accurate readings ofthc micrometer.

25. The micrometer of claim 24 wherein the resilient force applying means comprises a floating nut means spaced from, non-engaging with, and opposing said control nut and having threads mating with those of said threaded section. and a biasing means engaged with said nut means for urging said nut means against said spindle.

26. The micrometer of claim 23 wherein the spindle includes a ball tip and the anvil means includes a ball anvil head.

27. The micrometer of claim 1 wherein said micrometer is a direct reading micrometer for measuring workpieces of O to 2 inches.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 845 564 Dated November 5th, 1974 Inven Paul A. Morgan 7 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 21, line 38, change "mal" to --nal; line 39, change- "sloopy" to sloppy-; line 54, before. "engagement" insert -tight.

Column 22, line 36, after. "section" insert (comma). Column 23, line 17, after "ing" insert -pressure at said measuring position for each measurement that the micrometer makes. Column 24, line 1, change "continously" to --continuously.

Signed and sealed -this 4th day of February 1975.

(SEAL) I Attest:

- McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents uscoMM-nc eosn-Pan U. 5. GOVERNMENT PRINTING OFFICE I9. 0-386-334.

FORM P D-1050 (10-69) 

1. A micrometer for measuring a workpiece comprising: a. a frame having an anvil mounting section and a spindle mounting section, the anvil mounting section being connected to the spindle mounting section for relative movement thereto; b. a spindle mounted in said spindle mounting section for axial movement; c. an anvil means mounted to said anvil mounting section and movable relative to said spindle and anvil mounting sections from a non-measuring position to a measuring position upon the creation of a gauging pressure by a workpiece that is being measured between the anvil means and the spindle; d. indicating means responsive to the relative movement of the anvil means for indicating movement of said anvil means to the measuring position; e. a first biasing means for biasing said anvil means for movement relative to said mounting sections and for maintaining the same amount of gauging pressure at said measuring position for each measurement that the micrometer makes; and f. a second biasing means connecting said mounting section and spindle mounting section for controlling the relative movement of the anvil mounting section to the spindle mounting section and absorbing gauging pressure in excess of that which can be absorbed by said first biasing means.
 2. The micrometer of claim 1 wherein said anvil means includes a measuring arm and said biasing means is a spring engaged with said measuring arm.
 3. The micrometer of claim 2 wherein said measuring arm is pivotally mounted to said anvil mounting section and said spring urges said measuring arm toward said non-measuring position.
 4. The micrometer of claim 1 where said anvil mounting section is pivotally connected to said spindle mounting section.
 5. The micrometer of claim 4 wherein said second biasing means comprises a bolt mounted in said anvil mounting section and having one end captured in said spindle mounting section, a spring mounted about said bolt in said spindle mounting section, and an abutment fixed to and movable with said anvil mounting section for compressing said spring to absorb excess gauging pressure.
 6. The micrometer of claim 1 wherein said indicating means comprises a sensing means for sensing movement of said anvil means and an indicator responsive to said sensing means for indicating movement of the anvil means to the measuring position.
 7. The micrometer of claim 6 wherein said seNsing means comprises a pair of contacts actuated by movement of said anvil means, and said indicator is a light in circuit with said contacts.
 8. The micrometer of claim 1 wherein said indicating means comprises an electric circuit including a light operated upon movement of said anvil means to the measuring position.
 9. The micrometer of claim 1 including a gear mounted on said spindle and having gear teeth, and a drive sleeve having internal gear teeth engaged with the gear teeth of said gear for rotating the spindle and causing it to move axially, said drive sleeve having a control knob extending exteriorly of said spindle mounting section to enable rotation of the drive sleeve.
 10. The micrometer of claim 9 wherein the portions of the internal gear teeth of the drive sleeve and the portions of the gear teeth of said gear that mate with each other have the same shape.
 11. The micrometer of claim 10 wherein said intermal gear teeth are larger than the gear teeth of the gear to produce a sloopy fit of the drive sleeve with said gear.
 12. The micrometer of claim 9 wherein the internal gear teeth of the drive sleeve extend exteriorly of the spindle mounting section into the control knob to permit the spindle to be withdrawn from the anvil means and to extend exteriorly of the spindle mounting section.
 13. The micrometer of claim 1 wherein the spindle has a threaded section, a control nut extends partially around a longitudinal portion of the threaded section and has threads mating with those of the threaded section of the spindle, and resilient force applying means acts transverse to the axis of the spindle to continuously urge the mating threads of the spindle and control nut into engagement with each other to maintain the roots and crests of the threads of the spindle in continuous longitudinal alignment with the roots and crests of the control nut and provide for accurate readings of the micrometer.
 14. The micrometer of claim 13 wherein the resilient force applying means comprises a floating nut means spaced from, non-engaging with, and opposing said control nut and having threads mating with those of said threaded section, and a biasing means engaged with said nut means for urging said nut means against said spindle.
 15. The micrometer of claim 14 wherein the biasing means engaged with said nut means is a coil spring.
 16. The micrometer of claim 14 including means for positioning said control nut at a set longitudinal distance from said anvil means when said anvil means is in its measuring position.
 17. A micrometer for measuring a workpiece comprising: a. a frame having an anvil mounting section and spindle mounting section; b. anvil means mounted to said anvil mounting section; c. a spindle threadably mounted in said spindle mounting section for axial movement; d. a gear mounted on said spindle and having gear teeth; and e. a rotatable drive sleeve having internal gear teeth engaged with the gear teeth of said gear for rotating said spindle and causing it to move axially, said drive sleeve having a control knob mounted externally of said spindle mounting section to enable rotation of the drive sleeve.
 18. The micrometer of claim 17 wherein the portions of the internal gear teeth of the drive sleeve and the portions of the gear teeth of said gear that mate with each other have the same shape.
 19. The micrometer of claim 18 wherein said internal gear teeth are larger than the gear teeth of the gear to produce a sloppy fit of the drive sleeve with said gear.
 20. The micrometer of claim 17 wherein the internal gear teeth of the drive sleeve extend exteriorly of the spindle mounting section into the control knob to permit the spindle to be withdrawn from the anvil means and to extend exteriorly of the spindle mounting section.
 21. The micrometer of claim 17 wherein the spindle has a threaded section a control nut extends partially around a longitudinal portion of the threaded section and has tHreads mating with those of the threaded section of the spindle, and resilient force applying means acts transverse to the axis of the spindle to continuously urge the mating threads of the spindle and control nut into tight engagement with each other to maintain the roots and crests of the threads of the spindle in continuous longitudinal alignment with the roots and crests of the control nut and provide for accurate readings of the micrometer.
 22. The micrometer of claim 21 wherein the resilient force applying means comprises a floating nut means spaced from, non-engaging with, and opposing said control nut and having threads mating with those of said threaded section, and a biasing means engaged with said nut means for urging said nut means against said spindle.
 23. A micrometer for measuring a workpiece comprising: a. a frame having an anvil mounting section and a spindle mounting section, said anvil mounting section being connected to said spindle mounting section for relative movement thereto; b. a spindle mounted in said spindle mounting section for axial movement; c. an anvil means mounted to said anvil mounting section and movable relative to said spindle mounting section from a non-measuring position to a measuring position upon the creation of gauging pressure by a workpiece that is being measured between the anvil means and the spindle, said anvil means including a measuring arm comprising a top section extending above the anvil mounting section and having an anvil head mounted thereon, said measuring arm further including a center section, means pivotally mounting said center section to the anvil mounting section and a bottom section offset from the top section and substantially enclosed by said anvil mounting section; d. indicating means responsive to the relative movement of the anvil means for indicating movement of said anvil means to the measuring position; and e. a spring engaged with said bottom section and anvil mounting section for biasing said anvil means for movement relative to the spindle mounting section and for maintaining the same amount of gauging
 24. The micrometer of claim 23 wherein the spindle has a threaded section, a control nut extends partially around a longitudinal portion of the threaded section and has threads mating with those of the threaded section of the spindle, and resilient force applying means acts transverse to the axis of the spindle to continously urge the mating threads of the spindle and control nut into tight engagement with each other to maintain the roots and crests of the threads of the spindle in continuous longitudinal alignment with the roots and crests of the control nut and provide for accurate readings of the micrometer.
 25. The micrometer of claim 24 wherein the resilient force applying means comprises a floating nut means spaced from, non-engaging with, and opposing said control nut and having threads mating with those of said threaded section, and a biasing means engaged with said nut means for urging said nut means against said spindle.
 26. The micrometer of claim 23 wherein the spindle includes a ball tip and the anvil means includes a ball anvil head.
 27. The micrometer of claim 1 wherein said micrometer is a direct reading micrometer for measuring workpieces of 0 to 2 inches. 